Detection of prostate-specific antigen- or prostate-specific membrane antigen-positive circulating cells in prostatic cancer patients: clinical implications.

OBJECTIVES: To evaluate the clinical benefit from using circulating prostate-specific antigen (PSA) and prostate-specific membrane antigen (PSM) mRNA detection in prostate cancer staging and in follow-up.
METHODS: Nested reverse transcriptase-polymerase chain reaction (RT-PCR) assays were performed on RNA extracted from blood drawn from 56 patients with prostate cancer before any treatment. Additionally, assays were done on posttreatment samples from 50 patients who were followed up by serum PSA level, to determine whether any relationship exists between RT-PCR results and tumor recurrence. The prostate cell specificity of assays was evaluated by analysis of 21 blood samples from women or cystoprostatectomized men.
RESULTS: With PSM RT-PCR assay, good sensitivity and prostate cell specificity could not be attained together, since high PSM mRNA illegitimate expression has been shown in some healthy donor bloods. For this reason, only PSA RT-PCR assay was used as a clinical marker. PSA mRNA was detected in peripheral blood of 4 out of 31 patients with clinically localized prostate cancer. It showed no relationship to the pathologic stage, but significant relationship to metastatic status, lymph node involvement and Gleason score. During follow-up, circulating PSA mRNA was detected in 8 out of 17 (47%) patients in treatment failure and in only 1 out of 33 (3%) successfully treated patients, with significant relationship between RT-PCR results and concomitant serum PSA levels.
CONCLUSION: Our study reveals no significant advantage to PSA RT-PCR assay (1) in improving the staging of clinically localized prostate cancer or (2) in follow-up treatment failure, as compared to the usual recurrence marker (serum PSA). Additional investigations are needed to determine the ultimate significance and the management of patients with positive PSA RT-PCR assays.